Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$82.40	8.520%	$89.4205	$89.42	$89.40	$89.40
Purchase #2	$91.44	3.766%	$94.8836	$94.88	$94.90	$94.90
Purchase #3	$212.71	3.628%	$220.4271	$220.43	$220.45	$220.40
Purchase #4	$167.89	12.367%	$188.653	$188.65	$188.65	$188.70
Purchase #5	$70.69	3.603%	$73.237	$73.24	$73.25	$73.20
Purchase #6	$91.55	7.104%	$98.0537	$98.05	$98.05	$98.10
Purchase #7	$55.57	13.153%	$62.8791	$62.88	$62.90	$62.90
7 purchase totals =	$772.25		$827.5540	$827.55	$827.60	$827.60